HomeRice Bran Solvent Extraction Plant

Rice Bran Solvent Extraction Plant

Rice Bran Solvent Extraction Plant

Rice bran is a by-product obtained during rice milling. It is the golden-reddish outer layer removed after husking and rice polishing. Rice bran contains 16-22% oil, which is recovered through a solvent extraction process. As rice bran is a floury material, it must be pelletized before solvent extraction.

The Solvent Extraction process involves injecting hexane into the oil-bearing material, creating a mixture of oil and solvent called miscella. Hexane in the miscella is later evaporated using a distillation unit, leaving unrefined oil. The evaporated hexane is condensed and recycled. Our innovative design techniques in continuous extractors and desolventizer toasters result in minimal hexane loss and have garnered client accolades. The by-product, known as de-oiled bran or de-oiled cake, is an excellent ingredient for cattle and poultry feed, as it contains proteins and other nutrients.

Pellet Preparatory Section

We ensure oil and meal quality through an efficient preparatory section design. Material preparation involves removing foreign materials and pretreating the bran with live steam using a paddle screw conditioner to make it suitable for pelletization.

Pelletization compresses the material into pellets. The conditioned raw material is pushed through a roller and pellet die to form pellets, which are then cooled with a horizontal conveying cooler. This cooling step ensures optimal solvent penetration into the oil-bearing material during extraction.

Extraction Section

Horizontal continuous extractors, used worldwide, operate on gravity percolation. The prepared material is transported to the extractor via a conveyor. Solvent sprayers spray the solvent across the raw material bed, moving it from the feed to the discharge end. The extractor bed, equipped with an efficient filtration system, holds the material and provides clean miscella, which then goes to heaters to separate hexane from oil in stages. Lighted sight glasses allow viewing of the spray distribution within the extractor.

The wet meal from the extractor is de-oiled but still contains absorbed solvent. It is transported by bulk flow conveyor to the desolventizing section for hexane recovery.

Desolventization

The desolventizer-toaster (DT) consists of a series of vertically mounted heating jackets. Each jacket has a double bottom for high-pressure steam, with open steam provision to ensure the material surface is fully treated.

De-oiled material from the extractor, containing 20-35% solvent, enters from the top of the desolventizer and passes through steam-heated stages while an agitator shaft with blades rotates it. The desolventization process involves direct and indirect heating to a temperature well above the solvent’s boiling point, ensuring no residual solvent remains in the de-oiled material. The material flows from one jacket to the next via discharge chutes, while solvent vapors are sent to condensers through a wet scrubber for washing.

The de-oiled, desolventized meal, known as de-oiled bran, is an excellent ingredient for cattle and poultry feed. It is conditioned and cooled to the desired moisture level before transport to the bagging section via conveyor.

Distillation

The miscella from the extractor contains approximately 12-18% solvent (for oil cakes or rice bran) and up to 25-35% for sunflower or rapeseed. These liquids are separated by evaporating the solvent, which has a lower boiling point (64-67°C), leaving pure oil.

The distillation occurs in three stages under vacuum (zero oxygen), retaining better oil characteristics. The first stage occurs in an economizer, followed by a flasher, which evaporates the solvent, leaving only oil. The oil is further treated with open steam to remove any residual solvent.

The produced solvent vapors pass through an oil vapor separator to capture any oil particles before moving to a condenser.

Condensation of Hexane

Hexane vapors from the desolventizing and distillation sections require condensation. Floating head-type condensers with tube bundles circulate cooling water through the tubes, with vapors outside. Solvent vapors cool and condense into liquid, which is then separated from water in a solvent-water separator and returned to the extractor. Uncondensed gases are directed to a contact cooler and washed with cold water spray.

Final Solvent Recovery

Residual air in the system may contain trace solvent vapor. To recover this, a final vent air stripping column with an absorber is used, which provides ample contact surface. Mineral oil in the absorber captures solvent vapors from the air. Residual vapors are evacuated through a vent condenser cooled by water in a closed circuit. The residual air is aspirated through an absorption tower where mineral oil absorbs any remaining hexane before condensation.

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